To be fair, Buzzie is correct to a certain degree. I also recall Nasser Hussain giving an explanation about the numbers on the caps. The player's selection number was on the side or back. The other number (under the ECB badge at the front if I remember correctly) denoted the number of caps for that player, however it was only the significant numbers i.e. if you'd played for England 50 times you had 50 on your cap.
If you had currently played 74, you kept the number 50 on your cap until the next milestone of 100, were you lucky/good enough to have been selected that many times.
Hope that clears things up a little!